Not Applicable.
Not Applicable.
The present invention relates in general to audio reproduction apparatus, and, more specifically, to randomizing the playback order of tracks from a prerecorded media.
The shuffle feature is a well known function of audio playback equipment wherein the order in which tracks on a prerecorded media are played back is randomized, thereby adding variety and unpredictability to a listening experience. Compact disc audio (CD-audio) players in particular have led to widespread use of the shuffle feature.
Rather than use a truly random selection of a next track to be played, it is known that most users prefer a random order in which a single track is not played a second time until all tracks have been played once. In the past, this has required either 1) storing an entire sequence in memory to ensure that a track is not replayed, or 2) processing using repeated application of arithmetic operations (such as shifting, scaling, etc.) which do not always produce an acceptable result and may have to be repeated until an acceptable sequence is obtained. Thus, an improved method of generating a shuffle sequence is desired.
As mechanisms for handling and reading compact discs (CDs) have been miniaturized, the use of multiple-disc CD changers has grown. When shuffling the playback order across multiple discs, however, the prior art has generated shuffle sequences in which track locations between different discs does not affect the sequence (i.e., it is as though all the tracks were on one big disc). The resulting frequent changing of discs between random selections may not match users preferences. Thus, an improved method of shuffling tracks across multiple discs is also needed.
The present invention has the advantages of generating shuffle sequences which are always valid, do not repeat tracks while there are tracks that have not yet been played, and do not require complex processing. When shuffling across multiple discs, a more natural and consistent operation is obtained.
One primary aspect of the invention for achieving these results includes a method of determining a shuffle sequence for playing tracks from a prerecorded media. A modulus m is determined that is greater than or equal to the total number of tracks T to be randomized in the shuffle sequence. The tracks are stored on the prerecorded media in a predetermined order xi, where i is an index. A multiplier a is determined for which (axe2x88x921) is a multiple of every prime number less than m that is a factor of m, wherein if m is a multiple of 4 then (axe2x88x921) is also a multiple of 4. An increment c is determined which is relatively prime with m. The shuffle sequence is determined in response to a linear congruential random number generator using m, a, and c.